Subscriber network terminal of an access line network and method for operating a network connecting unit

ABSTRACT

A subscriber side network termination unit of an access line network and method for operating same having: (a) first interface for the access line network-side transmission and reception of a transmission frame containing data channels: (b) a second interface for the subscriber-side offering of telecommunication payload data channels for telecommunication applications as well as a signaling channels, and (c) a third interface for the subscriber-side offering of data channels for data applications. The signaling channel; of the second interface is employed for the transmission of signaling data for the transmission of payload data via the second interface or the third interface.

The present invention is directed to a subscriber-side networktermination unit and method of operating some of an access line networkhaving: (a) an interface for the access line network-side transmissionand reception of a transmission frame with a plurality of data channels,including a signaling channel,: (b) an interface for the subscriber-sideoffering of telecommunication payload data channels fortelecommunication applications as well as a signaling channel allocatedto these telecommunication payload data channels; and: (c) an interfacefor the subscriber-side offering of data channels for data applications.

DESCRIPTION OF THE PRIOR ART

In the subscriber access area, modern telecommunication networks havedigital access line networks available to them that connect one or morelocal switching centers to subscriber terminal equipment via subscriberline networks and subscriber-side network termination units. Access linenetworks were originally designed for the transmission of low-frequencyinformation signals such as, for example, in analog telephony or in theemployment of narrow band services. The bit rate transmitted at thesubscriber side in the access line network is thereby defined, forexample for a narrow band ISDN basic access, such that the longestsubscriber lines that occur still can be used. Apart from data rates of16 kbit/s employed for synchronization and echo suppression purposes,the narrow band ISDN basic access, which is also referred to as BA (fromthe English expression “Basic Access”), has a data rate of 144 kbit/sdivided into a control channel referred to as D-channel with 16 kbit/sand into two payload channels of 64 kbit/s each that are referred to asB-channels. As a result of this dimensioning basis, a large part of thebit rate that can be maximally dependably transmitted, i.e. of themaximum band width in the access line network area with shortersubscriber lines, remains unused. The degree of attenuation forsymmetrical double leads of copper subscriber lines that limits therange of the digital signal transmission, increases with the linelength. It is generally valid that the bit rate to be transmitted over asubscriber line can be all the higher the shorter the length of thissubscriber line. Access line networks designed for narrow band services,consequently, are also suitable for the transmission of more broad bandservices. Methods have thus prevailed in recent years with which theexisting copper lines in the access line network can be utilized for thetransmission of digital information signals.

Vittorio Ferretti, Guillermo Wichmann, “Mehrfachnutzung vonTeilnehmeranschlubkabeln”, Telecom Report, 14 (1991), No. 3, pages150-153 discloses a method for dividing the payload data rate of anISDN-BA of 144 kbit/s into a control channel referred to as D-channeland, optionally, two payload channels each having 32 kbit/s and apayload channel having 64 kbit/s data rate, preferably provided for dataapplications, or four payload channels each having a 32 kbit/s datarate. Although the plurality of applications, terminal equipment orsubscribers connectable via a line pair and a specific networktermination unit is increased, the data rate that is available for anapplication is reduced compared to an ISDN BA or remains of the samesize in the best case.

The connection of data processing equipment such as, for example, acomputer or an LAN to an access line network of a communication networkusually occurs for small companies or private households via a modem anda switched analog or digital connection, or via an ISDN connectionhaving a maximally obtainable data rate of 128 kbit/s.

The patent application DE 196 25 385 3, which was not yet published asof the priority date of the present application, discloses a method forthe transmission of information signals in an access line network viasubscriber lines, whereby transmission parameters of the subscriber lineare measured and settings are undertaken at the exchange side and at thesubscriber side based on the criterion of the measured results. Thesesettings, for example, are the bit rate that can be maximally dependablytransmitted and, potentially, the transmission method. As a resultthereof, bit rate and transmission method can be adaptively undertakenline-individually dependent on the physical transmission parameters. Inaddition to a D-channel with a band width of 16 kbit/s, it thus becomespossible to transmit even more payload channels wherein each channel hasa band width of 64 kbit/s. The maximum plurality of transmittablepayload channels is thereby dependent on the band width of theindividual subscriber line configuration, particularly on the length ofthe subscriber line.

To provide an information transport frame divided into time slots ofequal size is known as a method for the subscriber-side informationtransmission in such access line networks. Such method is known from thearticle by M. N. Huber and P. J. Kühn, “Modelling of a Multi-QueuePolling System with Arbitrary Server Interrupts for the Idle-SlotConcatenation Packet Switching Principle in a Hybrid CS/PS Node”,Proceedings of the 12th International Teletraffic Congress, Torino,1988. Each of these time slots is occupied either with switching systemdata (CS data based on the English expression “Circuit Switching”) orwith packet data (PS data from the English expression “PacketSwitching”), whereby all prime slots not occupied with switching systemdata are combined to form a remaining packet data transport channel(idle slot concatenation). The traffic type with which the remainingpacket data transport channel is occupied, for example ATM orLAN/Ethernet, is determined by the connection configuration,particularly by the packet data protocol that can be processed by theprotocol evaluation means of the subscriber side.

A patent application by the same assignee that was not published as ofthe filing date of this application discloses a method for asubscriber-side information transmission in an access line network withthe assistance of an information transport frame divided into time slotsof equal size, wherein at least some of these time slots are payloadchannel time slots whereof each is occupied either with switching systemdata or with packet data and all payload channel time slots not occupiedwith switching system data are combined to form a remaining packet datatransport channel. A protocol discriminator that enables an unambiguousallocation of the data contained in a time slot of the remaining packetdata transport channel to a traffic type is inserted into every timeslot of the remaining packet data transport channel, so that a protocolevaluation that is specific to a traffic type can be respectivelyundertaken at the reception side. This enables the utilization of theremaining packet data transport channel, which is also called ISCchannel or idle slot concatenation channel, by different traffic typessuch as, for example, ATM and LAN. As warranted, a length particularinserted per message additionally can be communicated given messages ofvariable length. For the transmission of variable-length messages,another version of such a method provides that a time slot of theremaining packet data transport channel not be occupied between twomessages in the remaining packet data transport channel. A time slot ofthe information transport frame thereby also can be used for framecontrol, and one time slot can be employed for ISDN signaling, whereinthese time slots provided for the transmission of control informationpreferably are arranged at permanently defined locations within theinformation transport frame.

An object of the present invention, therefore is to specify asubscriber-side network termination unit of an access line network thatadapts an access line network offering a plurality of payload channelsto subscriber applications in order to enable a more flexibleutilization of such an access line network for telecommunicationapplications and data applications. Moreover, a method for operatingsuch a network termination unit also should be specified.

SUMMARY OF THE INVENTION

The present invention defines a subscriber-side network termination unitof an access line network having: (a) a first interface offered by anaccess line interface control for the access line network-sidetransmission and reception of a transmission frame containing aplurality of data channels, including a signaling channel; (b) a secondinterface offered by a telecommunication interface control for thesubscriber-side offering of telecommunication payload data channels fortelecommunication applications as well as a signaling channel allocatedto these telecommunication payload data channels; and (c) a thirdinterface offered by a data interface control for the subscriber-sideoffering of data channels for data applications.

An inventive method for operating such a subscriber-side networktermination unit provides that, before the transmission of payload datavia either the second or third interfaces, signaling data respectivelyallocated to the payload data are transmitted via the signaling channelof the interface offered by the telecommunication interface control.

An inventive subscriber-side network termination unit that enables theimplementation of such a method, but also reflects an aspect of thepresent invention independently of such method, contains a controldevice for enabling a data transmission via the data interface controlafter a signaling allocated to this data transmission has occured viathe signaling channel of the second interface.

As a result of the inventive method, and in the inventive,subscriber-side network termination unit, the signaling channel of thesecond interface is employed both as signaling channel for thetelecommunication payload data channels of the second interface and as asignaling channel for the payload data channels of the third interface.This enables the simple imaging of the two subscriber-side interfacesonto a single access line network-side interface having only onesignaling channel, wherein a signaling channel, namely that of thesecond interface, is available as needed for each of the subscriber-sideinterfaces. Since a signaling channel is usually required only for abrief time, namely during the signaling phase, and signaling data areunproblematical in view of delay times, one signaling channel alsosuffices for two interfaces.

In an embodiment of the method of the present invention, it is providedthat the data interface control controls the transmission of signalingdata allocated to payload data to be transmitted via the third interfacevia the signaling channel of the interface offered by thetelecommunication interface control before these payload data aretransmitted via the third interface. A control of the transmission ofthe signaling data provided for data of the third interface via thesignaling channel of the second interface makes it possible that thedata application, for example a computer or a LAN with connectedcomputers, need access the subscriber-side network termination unit onlyvia a single interface, namely the third interface. An alternativeembodiment of such a method requires that the data application accessesthe subscriber-side network termination unit via the third interface andaccesses at least via the signaling channel of the second interface. Theaccess via the second interface can thereby occur, for example, byoperating the data application as communication terminal equipment atthe second interface.

Another embodiment of the inventive method provides that datatransmitted into the telecommunication payload data channels of thesecond interface at the subscriber side are only transmitted in specificdata channels in the access line network-side transmission frame. As aresult thereof, a fixed allocation of the payload data channels of thesecond interface to data channels of the transmission frame of the firstinterface and, thus, a simple conversion between channels of thissubscriber-side interface and channels of the access line network-sideinterface is enabled. It is thereby preferred that the signaling channelof the second interface also is permanently allocated to either a datachannel or a signaling channel of the transmission frame of the firstinterface.

An advantageous development of this aspect of the present inventionprovides that data transmitted at the subscriber side in the datachannels of the third interface are preferably transmitted in the accessline network-side transmission frame in free data channels not providedfor the transmission of subscriber-side data transmitted in thetelecommunication payload data channels of the second interface. Thisalso enables a fixed allocation of specific data channels of thetransmission frame of the first interface to the data channels of thethird interface and, thus, a facilitated conversion method between theseinterfaces.

A consistently fixed allocation of all data channels of the thirdinterface to data channels of the transmission frame of the firstinterface, however, could potentially greatly limit the band width or,respectively, data rate made available for data applications. A modifiedembodiment of this aspect of the present invention therefore providesthat data transmitted subscriber-side in the data channels of the thirdinterface are also transmitted in the data channels provided for thetransmission of subscriber-side data transmitted in thetelecommunication payload data channels of the second interface wheninadequate data channels provided for the transmission ofsubscriber-side data transmitted in the telecommunication payload datachannels of the second interface are not free in the access linenetwork-side transmission frame for these data. When, given such adevelopment of the present invention, adequate band width is not madeavailable for a data application by data channels of the transmissionframe of the first interface permanently allocated to the data channelsof the third interface, data channels of the transmission frame of thefirst interface permanently allocated to the payload data channels ofthe second interface also are employed for the transmission of payloaddata of the third interface. A data channel of the transmission frame ofthe first interface potentially allocated to the signaling channel ofthe second interface is not employed for the transmission of payloaddata of the third interface since this signaling channel is alsorequired for the third interface.

I an embodiment of the subscriber-side network termination unit, it isprovided that the second interface offers two telecommunication payloaddata channels for telecommunication applications at the subscriber side.When, in particular, the two telecommunication payload data channelsoffered by the second interface respectively have a data rate of 64kbit/s in a development of such an embodiment of a subscriber-sidenetwork termination unit and the signaling channel offered by the secondinterface has a data rate of 16 kbit/s, this interface corresponds to astandardized interface according to narrow band ISDN that is referred toas So interface.

Another embodiment of the subscriber-side network termination unitprovides that the first interface offers a transmission frame at theaccess line network side having a plurality of data channels with arespective data rate of 64 kbit/s. The conversion of the access linenetwork-side data channels into the payload data channels of thesubscriber-side, second interface with the same transmission ratethereby can be very simply implemented and is reduced to a purelyphysical conversion given a fixed channel allocation.

Additional features and advantages of the present invention aredescribed in, and will be apparent from, the Detailed Description of thePreferred Embodiments and the Drawing.

DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic block diagram of the subscriber-side networktermination unit in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The exemplary embodiment of the invention subscriber-side networktermination unit of an access line network shown in FIG. 1 in the formof a schematic block illustration contains a line interface LS as firstinterface (shown at the bottom in the figure) offered by an access lineinterface control referenced with framework unit RE, the line interfaceLS being provided for the access line network-side transmission andreception of a transmission frame containing a plurality n of datachannels. The individual data channels of this transmission framerespectively have a data rate of 64 kbit/s. A control channel with adata rate of 16 kbit/s is contained in one of these data channels but,alternatively, also can be additionally contained in the transmissionframe. This network termination unit also contains an interface Sooffered by a telecommunication interface control referenced as BA unit,the interface So being provided for the subscriber-side offering oftelecommunication payload data channels for telecommunicationapplications TE1, TE2, TE8. The second interface So corresponds to astandardized ISDN interface of the type So with two B-channels of 64kbit/s data rate each and one D channel having a data rate of 16 kbit/s.Over and above this, the network termination unit contains an interfaceIT offered by a data interface control referenced as Internet unit asthird interface for the subscriber-side offering of data channels fordata applications.

In the illustrated exemplary embodiment, the data interface control IEaccesses the D-channel of the second interface So like atelecommunication application TE1. An interworking for the conversion ofdata to be transmitted at the subscriber side, and data to betransmitted at the access line network side, is provided between thetelecommunication interface control BA or, respectively, the datainterface control IE and the access line interface control RA. A bussystem with time slot structure is preferably provided for this purpose.Before the transmission of payload data via the second interface So,signaling data allocated to the payload data are transmitted via thesignaling channel D-channel of this interface So offered by thetelecommunication interface control BA.

In a first development of this exemplary embodiment, signaling dataallocated to the payload data are transmitted via the signaling channelD-channel of the second interface So offered by the telecommunicationinterface control BA before the transmission of the payload data via thethird interface IT.

In a second development of this exemplary embodiment, the data interfacecontrol IE contains a control mechanism for enabling a data transmissionvia this data interface control IE after a signaling allocated to thisdata transmission has occurred via the signaling channel D-channel ofthe second interface So.

A third, preferred development of this exemplary embodiment includesboth of the characteristics respectively described above for the firstand second development of the exemplary embodiment. Features describedbelow apply to all such developments.

The employment of the signaling channel D-channel of the secondinterface So for the transmission of signaling data for the transmissionof payload data both via the second interface So and via the thirdinterface IT is to be considered a special characteristic of thedisclosed, subscriber-side network termination unit.

The telecommunication interface control BA unit converts the payload andsignaling information of the transmission frame into the So format or,respectively, converts the payload and signaling information of thesecond interface So into the transmission frame. The telecommunicationinterface control BA only can access the first and second payload datatime slot of the transmission frame. With respect to the secondinterface So, consequently, only functions of the physical layer, i.e.functions of the layer 1 according to the OSI reference model, areimplemented in the subscriber-side network termination unit. The secondinterface So makes all features of an ISDN-BA available at thesubscriber side.

For example, a local data network LAN having a plurality of dataapplications or an Internet terminal equipment can be connected to thethird interface IT. However, some other terminal equipment with aconstant data stream also can be connected. The third interface IT can,for example, be a standardized Ethernet interface. When a dataapplication accessing the third interface IT becomes active, the datainterface control IE sets up a connection via the D-channel of thesecond interface So per signaling. The following information transferoccurs between the data interface control IE and the access lineinterface control RE. Consequently, the signaling, in fact, occurs viathe second interface So but not the data transmission. As a resultthereof, the data transmission is not limited to twice 64 kbit/s but,dependent on the band width of the first interface LS and, consequently,on the band width of the third interface IT can, for example, amount to12*64 kbit/s.

The data interface control IE of the broad band, third interface ITnormally does not occupy the first and second payload data time slot ofthe transmission frame of the first interface LS. As a result thereof, acommunication of telecommunication applications TE2, TE8 via the secondinterface So also is possible given operation of the third interface IT.When the remaining payload data time slots of the transmission frame ofthe first interface LS, however, do not offer enough band width for theneeds of the data transmission provided via the third interface IT, thedata interface control IE of the broad band, third interface IT alsoaccesses the first and/or second payload data time slot of thetransmission frame of the first interface LS not blocked by the existingtelecommunication applications [sic] TE2, TE8 via the second interfaceSo. Although the present invention has been described with reference tospecific embodiments, those of skill in the art will recognize thatchanges may be made thereto without departing from the spirit and scopeof the invention as set forth in the hereafter appended claims.

I claim:
 1. A method for operating a subscriber-side network terminationunit of an access line network, the method comprising the steps of:providing the termination unit with a first interface offered by anaccess line interface control for access line network-side transmissionand reception of a transmission frame containing a plurality of datachannels including a signal channel; providing the termination unit witha second interface offered by a telecommunication interface control fora subscriber-side offering of both telecommunication payload datachannels for telecommunication applications and a signal channelallocated to the telecommunication payload data channels; providing thetermination unit with a third interface offered by a data interfacecontrol for the subscriber-side offering of data channels for dataapplications; and transmitting signaling data respectively allocated topayload data via the signaling channel of the second interface offeredby the telecommunication interface control before the transmission ofthe payload data via the second interface or the third interface, andcontrolling the transmission of the signaling data, via the datainterface control, before the transmission of the payload data via thethird interface.
 2. A method for operating a subscriber-side networktermination unit of an access line network as claimed in claim 1,wherein data transmitted at the subscriber-side in the telecommunicationpayload data channels of the second interface are only transmitted inspecific data channels in the access line network-side transmissionframe.
 3. A method for operating a subscriber-side network terminationunit of an access line network as claimed in claim 2, wherein the datatransmitted at the subscriber-side in the data channels of the thirdinterface are transmitted in the access line network-side transmissionframe in free data channels not provided for the transmission of thedata transmitted at the subscriber-side in the telecommunication payloaddata channels of the second interface.
 4. A method for operating asubscriber-side network termination unit of an access line network asclaimed in claim 3, wherein the data transmitted at the subscriber-sidein the data channels of the third interface is further transmitted indata channels provided for the transmission of the subscriber-side datatransmitted in the telecommunication payload data channels of the secondinterface when enough data channels provided for the transmission of thesubscriber-side data transmitted in the telecommunication payload datachannels of the second interface are not free in the access linenetwork-side transmission frame for the subscriber-side data.
 5. Asubscriber-side network termination unit of an access line network,comprising: a first interface offered by an access line interfacecontrol for access line network-side transmission and reception of atransmission frame containing a plurality of data channels including asignaling channel; a second interface offered by a telecommunicationinterface control for a subscriber-side offering of bothtelecommunication payload data channels for telecommunicationapplications and a signaling channel allocated to the telecommunicationpayload data channels; a third interface offered by a data interfacecontrol for the subscriber-side offering of data channels for dataapplications; and a controller for enabling a data transmission via thedata interface control after a signaling allocated to the datatransmission has occurred via the signaling channel of the secondinterface, wherein the controller is integrated in the data interfacecontrol which, before the transmission of the payload data via the thirdinterface, controls the transmission of the signaling data.
 6. Asubscriber-side network termination unit of an access line network asclaimed in claim 5, wherein the second interface offers twotelecommunication payload data channels for the telecommunicationapplications at the subscriber side.
 7. A subscriber-side networktermination unit of an access line network as claimed in claim 6,wherein the two telecommunication payload data channels offered by thesecond interface respectively have a data rate of 64 kbit/s, and thesignaling channel offered by the second interface has a data rate of 16kbit/s.
 8. A subscriber-side network termination unit of an access linenetwork as claimed in claim 5, wherein the first interface offers atransmission frame at the access line network side having a plurality ofdata channels, each of the plurality of data channels having arespective data rate of 64 kbit/s.